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Question bank

Frontier AI technical interview question bank.

Practice coding, system design, behavioral, and project questions for frontier AI roles.

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Frontier Rehearsal · Independent practice · Not affiliated with OpenAI, Anthropic, or xAI.

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Home
Question bank

Frontier AI technical interview question bank.

Practice coding, system design, behavioral, and project questions for frontier AI roles.

Company

FREE PRACTICE

Public demos, always pinned.

Start with either demo. They remain here when you filter or sort.

Free account: sign in to practice the marked Free questions.

Newest published questions; deterministic, never randomized.

Demo 1Number search with delayed feedback
Demo 2Design real-time device monitoring and control

Question bank filters

Reset filters

Question groups

Filter question bank by interview groupAll 269 Coding 162 System design 48 Behavioral 29 Hiring manager 16 Project deep dive 14

Topics

Filter question bank by topic tagsAll 269 Python 161 Algorithms 40 Data structures 46 Concurrency 27 Distributed systems 7 Storage & state 43 Networking 7 Reliability 30 ML / AI 27 Data / SQL 24 Security 7 Product design 25 Communication 66

Independent and not affiliated with the companies represented. Collected material does not predict future interview questions.

242 questions

Sort question bankSortFree first Newest Oldest AI ratio ↓AI ratio ↑

Question bank results

Every question has a public brief with the task, constraints, and follow-ups. Labels describe interactive practice access.

Free practice

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNot available

Resolve a cd target against a working directory

You are given an absolute working directory and the argument of a cd command. Return the absolute directory the shell would land in once ., .., and repeated separators are collapsed.

Practice focusRequirements - Line 1 is an absolute working directory; line 2 is the argument, which may be absolute or relative. - An absolute argument discards the working directory and is resolved from the root. - . keeps the current directory, .. moves to the parent, and climbing past the root stays at / . - Only a whole segment equal to . or .. is special; a name such as file..name remains one segment. - Return the path with one leading slash, no repeated or trailing separators, and / alone when nothing remains.…

Free practice

Topic tags
Python
Algorithms

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNot available

Palindrome after at most k deletions

Given a lowercase string and a deletion limit, decide whether removing at most that many characters can leave a palindrome while the surviving characters keep their order.

Practice focusRequirements - Line 1 is the string; line 2 is the integer limit. - Removing nothing is allowed, so a string that already reads the same in both directions always qualifies. - Each deletion is a single character, and characters that are kept never change position relative to each other. - On a mismatched pair, only two moves are worth trying: drop the left character or drop the right one. - Return true or false in lowercase, with no other text and no extra whitespace.…

Free practice

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNot available

Words ordered by a custom alphabet

An ordering is supplied as a permutation of the letters. Decide whether the given word list is sorted according to that ordering.

Practice focusRequirements - Line 1 is the word count; that many words follow one per line; the final line is the ordering, a permutation of the twenty-six lowercase letters. - The final line is always the ordering, so the count line only says how many words precede it. - Compare adjacent words left to right and stop at the first position where the letters differ; the letter ranked earlier wins. - If one word is a proper prefix of the other, the shorter word must appear first. - Return true or false in lowercase, with no other text.…

Free practice

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNot available

Segment text with a word list

Given a text and a small dictionary, decide whether the whole text can be written as a sequence of dictionary words, reusing a word as often as needed.

Practice focusRequirements - Line 1 is the text; line 2 is how many dictionary words follow, one per line. - Some inputs carry the two characters backslash and n instead of real line breaks; treat both forms as line separators before parsing. - Every character of the text must be covered in order by whole dictionary words; nothing may be skipped or reordered. - Words may be reused, and a word may be shorter than the remaining text but must match exactly at the current position. - Return true or false in lowercase, with no other text.…

New public brief

Topic tags
Storage & state
Product design

OpenAISystem design

Discussion / designResponse prompt

Reported interview periodSep 2026

Design real-time device monitoring and control

Design a service that ingests telemetry from many devices, detects meaningful state changes, and triggers control actions according to configurable rules.

Practice focusCover the ingestion API, event schema, message transport, stream processing, state storage, rule evaluation, and command-delivery path. Explain how the system handles bursty traffic, duplicate and out-of-order events, intermittent device connectivity, failed control commands, and service recovery. Define the latency and consistency guarantees you would offer, the metrics needed to operate the system, and the safeguards that prevent unstable feedback loops. Follow-ups 1. Support devices that remain offline for days and later upload buffered telemetry. 2.…

New public brief

Topic tags
Python

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodSep 2026

Number search with delayed feedback

A hidden integer lies in the inclusive range 1..n, where n >= 1. The test fixture supplies a check(x) callback. Your code must not implement the callback and is not given the hidden integer.

Practice focusEach call to check(x) submits a new integer guess in 1..n , but returns the comparison result for the previous submitted guess: - the first call returns None ; - -1 means the previous guess was too high; - 0 means the previous guess was correct; and - 1 means the previous guess was too low. Implement: Return the hidden integer. The fixture validates the answer and permits at most 2 n.bit length() calls to check . Track which guess each delayed response describes; do not apply a response to the newly submitted guess.…

New public brief

Topic tags
Python
Algorithms
Data / SQL

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Sep 2026

Implement 1-nearest-neighbor classification as a linear layer

You are given a matrix of labeled training examples and a batch of query examples. Implement squared-Euclidean 1-nearest-neighbor classification, then show that the same nearest-neighbor choice can be expressed…

Practice focusScenario You are given a matrix of labeled training examples and a batch of query examples. Implement squared-Euclidean 1-nearest-neighbor classification, then show that the same nearest-neighbor choice can be expressed as the output of an affine layer. For a query vector x and training vector x i : -||x - x i||² = 2x·x i - ||x i||² - ||x||² The final term is constant across all training examples for a fixed query, so it does not affect the winning index. This yields an affine score matrix with W = 2 X train.T and b i = -||x i||² .…

New public brief

Topic tags
Python
Algorithms

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Sep 2026

Infection Spread on a Grid

A grid contains healthy cells (0) and infected cells (1). Each day, infection spreads simultaneously from infected cells to their four orthogonal healthy neighbors. Return the number of days until every suscept…

Practice focusRequirements - All initially infected cells spread at the same time. - Return 0 when no healthy cell exists initially. - Do not allow newly infected cells to spread again during the same day. - Handle empty grids and validate rectangular input. - Target O(rows cols) time and space proportional to the active frontier. In the second stage, cells marked 2 are immune: they never change and block propagation. Follow-ups 1. Add recovery after a configurable number of days. 2. Require at least q infected neighbors before a cell changes. 3.…

New public brief

Topic tags
Python
Data structures

OpenAICodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Sep 2026

Aggregate Labels from Noisy Annotators

You receive labels from multiple annotators, with missing entries. Infer one binary label per item, identify annotators who systematically disagree with their peers, remove them, and recompute the labels.

Practice focusAssumptions Rows are annotators, columns are items, labels are 0 , 1 , or -1 for missing. Majority ignores missing entries and ties resolve to 1 . An annotator is bad when agreement with provisional labels on overlapping items is strictly below 0.5 . If gold is supplied, also return accuracy rounded to a stated precision. Requirements - Define behavior for items with no labels and annotators with no overlap. - Avoid treating missing values as votes. - Recompute the final majority after filtering. - State complexity and numerical representation.…

Public brief

Topic tags
Algorithms

OpenAICodingAI-generated

Talk-through codingNo local grader

Reported interview periodSep 2026

Deal and rank three-card poker hands

Implement the core of a three-card poker game. Cards are dealt to seated players one card at a time over three passes, then every hand is ranked and the winner or winners are returned.

Practice focusScenario Implement the core of a three-card poker game. Cards are dealt to seated players one card at a time over three passes, then every hand is ranked and the winner or winners are returned. Ranks increase from 2 through A . A deck contains one card for every rank and suit combination, and a card may be dealt at most once. Assumed interface The exact public API is intentionally flexible. One coherent option is: State any alternative interface before implementation.…

Public brief

Topic tags
Python

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Sep 2026

Expiring compute-credit ledger

Implement a ledger for compute-credit grants and debits whose events may arrive out of order.

Practice focusEach grant has a unique ID, amount, activation timestamp, and expiration duration. A grant is available through its expiration boundary. subtract(amount, timestamp) consumes credits that expire soonest. get balance(timestamp) returns the balance that would have been available at that point in time by evaluating all applicable events in chronological order. Define deterministic behavior for duplicate IDs, insufficient balance, equal timestamps, and late-arriving events. Preserve enough history to answer past-balance queries correctly. Follow-ups 1.…

Public brief

Topic tags
Communication

OpenAIHiring manager

Discussion / designResponse prompt

Reported interview periodNov 2025–Sep 2026

Motivation and impact conversation

Prepare a concise answer to each question:

Practice focus1. Why are you interested in this company and role now? 2. Which parts of the organization’s mission and work connect to your experience? 3. What positive and negative effects could advanced AI have on society? 4. How do safety and alignment considerations influence the way you build products or conduct research? 5. Describe one project that best demonstrates your judgment, ownership, and ability to learn. Use specific evidence from your own work. State your reasoning and trade-offs rather than relying on generic mission language.…

Public brief

Topic tags
Storage & state
Product design

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodFeb 2026–Sep 2026

Design a browser IDE for many users

Design a browser-based development environment where users can open persistent workspaces, edit files, run programs, and interact with a live terminal.

Practice focusCover workspace storage, process isolation, scheduling, standard-output streaming, terminal input, reconnect after refresh, dependency setup, and file synchronization. Explain how you prevent one user’s code from affecting another user or the host system. Address cold-start latency, idle-workspace suspension, resource quotas, long-running jobs, failure recovery, observability, and the trade-off between warm capacity and infrastructure cost. Follow-ups 1. Support collaborative editing without coupling file consistency to terminal I/O. 2.…

Public brief

Topic tags
Concurrency
Reliability
Product design

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodApr 2026–Sep 2026

Design a Long-Running Video Generation Platform

Design a service where users submit prompts for video generation. Jobs consume scarce accelerators, may run for minutes, can be cancelled, and must survive worker failure.

Practice focusRequirements - Define APIs for submit, status, progress streaming, cancel, retry, and result retrieval. - Queue and schedule jobs under per-user quotas, priorities, and accelerator constraints. - Use leases or heartbeats so abandoned work becomes recoverable. - Make retries safe, preserve checkpoints, and avoid publishing partial or duplicate results. - Store inputs and outputs securely with retention and content-safety controls. - Provide honest progress despite phases with uncertain duration.…

Public brief

Topic tags
Communication

OpenAIProject deep diveAI-generated

Discussion / designResponse prompt

Reported interview periodDec 2025–Sep 2026

Technical project deep dive

Lead a structured discussion of one technically substantial system you personally helped build. Choose a project with real constraints, meaningful decisions, and at least one outcome you can quantify. The goal …

Practice focusScenario Lead a structured discussion of one technically substantial system you personally helped build. Choose a project with real constraints, meaningful decisions, and at least one outcome you can quantify. The goal is to demonstrate engineering judgment and ownership, not to present a polished product pitch. Suggested structure 1. Context: Who used the system, what problem mattered, and what was explicitly out of scope? 2. Constraints: Scale, latency, reliability, privacy, staffing, deadlines, legacy dependencies, or cost. 3.…

Public brief

Topic tags
Python
Data structures
Concurrency
Networking

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodFeb 2026–Sep 2026

IPv4 and CIDR Iterator

Implement an iterator that walks IPv4 addresses from a seed, either forward, backward, or within the seed's CIDR block.

Practice focusRequirements - Accept a plain IPv4 address or CIDR such as 10.2.3.4/24 . - Include the seed as the first result. - Forward iteration ends at 255.255.255.255 or the block broadcast address. - Backward iteration ends at 0.0.0.0 or the block network address. - Validate octets, prefix lengths, and direction; raise StopIteration after exhaustion. - Use integer address arithmetic rather than incrementing dotted components as strings. State whether network and broadcast addresses are included; for this problem, include both boundaries. Follow-ups 1.…

Public brief

Topic tags
Concurrency
Storage & state
Security

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodFeb 2026–Sep 2026

Design an Online Chess Service

Design a service that matches two players, maintains authoritative legal game state, supports clocks, and allows games to be reviewed later.

Practice focusRequirements - Define APIs or real-time events for matchmaking, moves, resignations, draw offers, reconnects, and spectators. - The server—not the client—validates turns, legal moves, check, checkmate, stalemate, and special rules. - Make duplicate or reordered client messages idempotent. - Maintain fair clocks despite network delay and disconnects. - Persist an append-only move history and enough state for fast reconnect and review. - State scale assumptions, latency goals, and consistency boundaries.…

New public brief

Topic tags
Python

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Sep 2026

Generalized Tic-Tac-Toe

Implement a two-player game on a rows x cols board. A player wins by placing k consecutive marks horizontally, vertically, or along either diagonal.

Practice focusRequirements - Player 1 moves first and players alternate. - move places the current player's mark and returns that player number if the move completes a run of length k ; otherwise return 0 . - After a win, later calls return the existing winner without changing it. - Initially assume coordinates are valid and empty; explain how production code would reject invalid moves. - Support rectangular boards and k smaller than either dimension. - Avoid scanning the entire board after every move.…

New public brief

Topic tags
Python

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Sep 2026

Revenue Tracking with Direct Referrals

Build a customer revenue index. Each inserted customer has personal revenue and may name an existing customer as a referrer. A customer's total revenue is personal revenue plus the personal revenue of direct re…

Practice focusRequirements - Assign IDs starting at 0 in insertion order. - If a referrer is provided, update that customer's total by the new customer's personal revenue. - A customer's referrals do not contribute to its referrer's total; attribution is one level only. - The query considers totals at least min total revenue , orders by (total revenue, id) , and returns at most k IDs. - Validate non-negative revenue, valid referrers, and non-negative k .…

Public brief

Topic tags
Python
Data structures
Concurrency
Storage & state
Reliability

OpenAICodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodAug 2026–Sep 2026

Leased Work Queue with Dead-Letter Handling

Implement an in-memory queue whose jobs are reserved with expiring leases. A failed worker must not hold a job forever, and jobs that exceed their retry budget move to a dead-letter state.

Practice focusRequirements and assumptions - Jobs move among ready , reserved , completed , and dead . - reserve increments attempts and returns {item id, token} plus an internal deadline. - On explicit failure or lease deadline <= now , return the job to ready unless attempts reached max attempts ; then mark it dead. - Completion or failure with a stale token returns False without changing state. - Queue ready jobs deterministically and reject duplicate active IDs. - Validate positive limits and use the explicit clock supplied by callers. Follow-ups 1.…

New public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodMar 2026–Sep 2026

Evaluate an arithmetic string

Write solve(raw: str) -> str that evaluates one arithmetic expression and returns its integer value as text.

Practice focusRequirements - The expression contains non-negative integers, single spaces, and the operators + , - , , and / . There are no parentheses, no unary minus, and no exponentiation. - and / bind more tightly than + and - ; work left to right inside each precedence level. - / is integer division that truncates toward zero, so -3/2 truncates to -1 if a lead-in subtraction makes the intermediate negative. - Ignore every space and read the run of digits between operators as one number.…

Public brief

Topic tags
Product design

OpenAISystem design

Discussion / designResponse prompt

Reported interview periodJan 2026–Sep 2026

Design hold-then-charge payments

Design a payment platform with two operations:

Practice focus- hold synchronously requests authorization from a downstream card network and must return approval or rejection within a 500 ms p95 target. - charge references an approved hold, durably records the request, acknowledges it, and includes it in a later settlement batch. Assume 10 million holds and 8 million charges per day, peaks near 300 requests per second, 5–10 downstream networks, a two-hour nightly settlement window, and a seven-day hold lifetime.…

New public brief

Topic tags
Python
Data structures
Security

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Sep 2026

Minimize Encryption Work in a File Tree

A file hierarchy contains directories and files. Some files are already encrypted. You may encrypt an individual file or issue one recursive encryption request for an entire directory. Choose operations with mi…

Practice focusRequirements and cost model - Encrypting one file costs t req + t file . - Encrypting a directory costs t req + N t file , where N is every file in its subtree, including already-encrypted files. - A subtree with no unencrypted files costs 0 . - At a directory, you may batch the whole subtree or solve its children independently. count files returns (encrypted count, unencrypted count) . The input is a finite tree of FileNode and DirectoryNode objects, with boolean encryption flags, no cycles or shared nodes, and non-negative integer costs.…

Public brief

Topic tags
Python
Data structures
Distributed systems

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodOct 2025–Sep 2026

Aggregate Count and Topology over a Machine Tree

Machines form a rooted tree and may communicate only with their parent or children. Implement message handling so the root can count all machines and reconstruct a deterministic topology string.

Practice focusRequirements - A count request propagates to children; a leaf replies 1 ; an internal node replies with one plus all child counts. - A topology request produces id(child1,child2,...) ; a leaf is id[] . - Only the root publishes the final result. - Correlate replies with operation type and wait for every expected child exactly once. - Do not assume child replies arrive in order; sort by child ID for deterministic topology. - Avoid blocking the message handler and state behavior for duplicate requests.…

Previous5 of 11Next

Browse all original practice

Build a token-budget batcher
Sliding-window rate limiter
Interval calendar
Nested dictionary transforms
Command-log store
Dependency-ready scheduler
Streaming metric window
Evaluation slice aggregator
Build a reliable job runner
Build one adaptable decision story
Defend your role fit
Prepare one project deep dive
Design an evaluation artifact registry
Defend a reversible launch decision
Negotiate an ambiguous role scope
Trace a project from claim to evidence
Choose between two urgent priorities
Resolve a cross-functional disagreement
Own a consequential failure
Increase a team’s leverage
Warm a cold cache without a thundering herd
Ship a 500 GB checkpoint without a startup stampede
Make every document decision traceable to evidence
Share eight GPUs between two workloads with different promises
A mutable indexed sequence that must restart exactly
Trace a falling unit price to a rising bill
Keep a very long conversation usable while it streams
Design durable scheduled publishing
Make speculative code edits safe to accept
Recover a grouping rule from two-word phrases

CONTENT BOUNDARY

Independent frontier AI interview practice. Includes adaptations of collected interview material and original exercises; not official company questions and not affiliated with the companies represented. Collected material does not predict future interview questions. Report a correction.

Loading the question catalog…

FREE PRACTICE

Public demos, always pinned.

Start with either demo. They remain here when you filter or sort.

Free account: sign in to practice the marked Free questions.

Newest published questions; deterministic, never randomized.

Demo 1Number search with delayed feedback
Demo 2Design real-time device monitoring and control

Question bank filters

Reset filters

Question groups

Filter question bank by interview groupAll 269 Coding 162 System design 48 Behavioral 29 Hiring manager 16 Project deep dive 14

Topics

Independent and not affiliated with the companies represented. Collected material does not predict future interview questions.

242 questions

Sort question bankSortFree first Newest Oldest AI ratio ↓AI ratio ↑

Question bank results

Every question has a public brief with the task, constraints, and follow-ups. Labels describe interactive practice access.

Free practice

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNot available

Resolve a cd target against a working directory

You are given an absolute working directory and the argument of a cd command. Return the absolute directory the shell would land in once ., .., and repeated separators are collapsed.

Free practice

Topic tags
Python
Algorithms

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNot available

Palindrome after at most k deletions

Given a lowercase string and a deletion limit, decide whether removing at most that many characters can leave a palindrome while the surviving characters keep their order.

Free practice

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNot available

Words ordered by a custom alphabet

An ordering is supplied as a permutation of the letters. Decide whether the given word list is sorted according to that ordering.

Free practice

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodNot available

Segment text with a word list

Given a text and a small dictionary, decide whether the whole text can be written as a sequence of dictionary words, reusing a word as often as needed.

New public brief

Topic tags
Storage & state
Product design

OpenAISystem design

Discussion / designResponse prompt

Reported interview periodSep 2026

Design real-time device monitoring and control

Design a service that ingests telemetry from many devices, detects meaningful state changes, and triggers control actions according to configurable rules.

New public brief

Topic tags
Python

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodSep 2026

Number search with delayed feedback

A hidden integer lies in the inclusive range 1..n, where n >= 1. The test fixture supplies a check(x) callback. Your code must not implement the callback and is not given the hidden integer.

New public brief

Topic tags
Python
Algorithms
Data / SQL

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Sep 2026

Implement 1-nearest-neighbor classification as a linear layer

New public brief

Topic tags
Python
Algorithms

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Sep 2026

Infection Spread on a Grid

New public brief

Topic tags
Python
Data structures

OpenAICodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodJan 2026–Sep 2026

Aggregate Labels from Noisy Annotators

Public brief

Topic tags
Algorithms

OpenAICodingAI-generated

Talk-through codingNo local grader

Reported interview periodSep 2026

Deal and rank three-card poker hands

Implement the core of a three-card poker game. Cards are dealt to seated players one card at a time over three passes, then every hand is ranked and the winner or winners are returned.

Public brief

Topic tags
Python

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Sep 2026

Expiring compute-credit ledger

Implement a ledger for compute-credit grants and debits whose events may arrive out of order.

Public brief

Topic tags
Communication

OpenAIHiring manager

Discussion / designResponse prompt

Reported interview periodNov 2025–Sep 2026

Motivation and impact conversation

Prepare a concise answer to each question:

Public brief

Topic tags
Storage & state
Product design

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodFeb 2026–Sep 2026

Design a browser IDE for many users

Design a browser-based development environment where users can open persistent workspaces, edit files, run programs, and interact with a live terminal.

Public brief

Topic tags
Concurrency
Reliability
Product design

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodApr 2026–Sep 2026

Design a Long-Running Video Generation Platform

Design a service where users submit prompts for video generation. Jobs consume scarce accelerators, may run for minutes, can be cancelled, and must survive worker failure.

Public brief

Topic tags
Communication

OpenAIProject deep diveAI-generated

Discussion / designResponse prompt

Reported interview periodDec 2025–Sep 2026

Technical project deep dive

Public brief

Topic tags
Python
Data structures
Concurrency
Networking

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodFeb 2026–Sep 2026

IPv4 and CIDR Iterator

Implement an iterator that walks IPv4 addresses from a seed, either forward, backward, or within the seed's CIDR block.

Public brief

Topic tags
Concurrency
Storage & state
Security

OpenAISystem designAI-generated

Discussion / designResponse prompt

Reported interview periodFeb 2026–Sep 2026

Design an Online Chess Service

Design a service that matches two players, maintains authoritative legal game state, supports clocks, and allows games to be reviewed later.

New public brief

Topic tags
Python

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodDec 2025–Sep 2026

Generalized Tic-Tac-Toe

Implement a two-player game on a rows x cols board. A player wins by placing k consecutive marks horizontally, vertically, or along either diagonal.

New public brief

Topic tags
Python

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodNov 2025–Sep 2026

Revenue Tracking with Direct Referrals

Public brief

Topic tags
Python
Data structures
Concurrency
Storage & state
Reliability

OpenAICodingHalf AI-generated

Python codingWebAssembly + public tests

Reported interview periodAug 2026–Sep 2026

Leased Work Queue with Dead-Letter Handling

Implement an in-memory queue whose jobs are reserved with expiring leases. A failed worker must not hold a job forever, and jobs that exceed their retry budget move to a dead-letter state.

New public brief

Topic tags
Python

MetaCoding

Python codingWebAssembly + public tests

Reported interview periodMar 2026–Sep 2026

Evaluate an arithmetic string

Write solve(raw: str) -> str that evaluates one arithmetic expression and returns its integer value as text.

Public brief

Topic tags
Product design

OpenAISystem design

Discussion / designResponse prompt

Reported interview periodJan 2026–Sep 2026

Design hold-then-charge payments

Design a payment platform with two operations:

New public brief

Topic tags
Python
Data structures
Security

DatabricksCoding

Python codingWebAssembly + public tests

Reported interview periodApr 2026–Sep 2026

Minimize Encryption Work in a File Tree

Public brief

Topic tags
Python
Data structures
Distributed systems

OpenAICoding

Python codingWebAssembly + public tests

Reported interview periodOct 2025–Sep 2026

Aggregate Count and Topology over a Machine Tree

Machines form a rooted tree and may communicate only with their parent or children. Implement message handling so the root can count all machines and reconstruct a deterministic topology string.

Previous5 of 11Next

Browse all original practice

Build a token-budget batcher
Sliding-window rate limiter
Interval calendar
Nested dictionary transforms
Command-log store
Dependency-ready scheduler
Streaming metric window
Evaluation slice aggregator
Build a reliable job runner
Build one adaptable decision story
Defend your role fit
Prepare one project deep dive
Design an evaluation artifact registry
Defend a reversible launch decision
Negotiate an ambiguous role scope
Trace a project from claim to evidence
Choose between two urgent priorities
Resolve a cross-functional disagreement
Own a consequential failure
Increase a team’s leverage
Warm a cold cache without a thundering herd
Ship a 500 GB checkpoint without a startup stampede
Make every document decision traceable to evidence
Share eight GPUs between two workloads with different promises
A mutable indexed sequence that must restart exactly
Trace a falling unit price to a rising bill
Keep a very long conversation usable while it streams
Design durable scheduled publishing
Make speculative code edits safe to accept
Recover a grouping rule from two-word phrases

CONTENT BOUNDARY